1. Field of the Invention
The present invention pertains generally to a device and a method for verifying correct operation (safety testing) of medical pacer (also known as "pacemaker") devices. The present invention pertains more particularly to a method and a device for testing pacemakers utilizing a portable self-contained microcomputer-based pacemaker testing device capable of performing comprehensive safety testing of pacemakers at any desired location, eliminating the prior art need for complex and expensive additional testing equipment, which further provides a significant reduction in the amount of time necessary to comprehensively test the pacemakers.
2. Description of the Prior Art
Medical pacing equipment can be generally divided into two types, that which is implanted internally into the body, and that which is maintained externally to the body. While the present invention can be modified to test all types of medical pacing equipment, the present invention is particularly well-suited to the testing of external medical pacing equipment, and is most particularly well-suited to the testing of external cardiac pacemakers.
A specific type of medical pacer is the cardiac pacemaker. Cardiac pacemakers are devices that provide an electrical stimulus to the heart muscle at regular intervals. Application of the stimuli is through appropriate lead wires and electrodes causing the heart muscle to contract. Cardiac pacemakers can be either implanted internally within the body or utilized externally to the body.
External cardiac pacing is routinely employed in hospitals to temporarily alleviate cardiac dysfunction following trauma, heart attack, major surgery or until a permanent pacemaker can be implanted.
Two common types of external cardiac pacemakers are the ventricular demand and atrio-ventricular sequential demand type pacemakers. The first is designed to generate stimuli that are applied to the ventricles of the heart (ventricular external demand pacemakers) causing the ventricles to contract. The second type of cardiac pacemaker is designed to generate two sequential stimuli, one applied to the atria and the other applied to the ventricles so that these contract in sequence (atrio-ventricular (A-V) sequential external demand pacemakers).
As with all clinical instrumentation, external cardiac pacemakers must be routinely checked as a safety precaution in order to assure proper performance and calibration. This responsibility is borne by the clinical engineering department in a typical health care facility.
The testing of external cardiac pacemakers may be generally separated into two types of testing, a relatively quick operational test that is performed on a regular basis, and a more comprehensive detailed testing procedure that is also performed on a regular, though less frequent, basis.
The testing of external cardiac pacemakers must be carefully performed, and the Emergency Care Research Institute (ECRI), an established advisor to the medical profession, has established recommended safety and performance standards for external pacemakers. Additionally, the manufacturers of external cardiac pacemakers also often provide "checkout manuals" for their external pacemaker products which specify the necessary test procedures for verifying both programmable and fixed parameters.
Although it may be subject to change from time to time, one recommended external cardiac pacemaker comprehensive testing procedure comprises a battery of tests including, but not limited to: 1) pulse duration; 2) pulse amplitude; 3) pulse rate; 4) sensitivity; 5) rate compensation; 6) refractory intervals (stimulus and sensed); and where the pacemaker is an atrio-ventricular sequential pacemaker, 7) atrio-ventricular (A-V) delay intervals. In an A-V sequential pacemaker, the first six tests are measured for each of the atrial and ventricular stimulation circuitries; the seventh test measures timing between atrial and ventricular pacing pulses. Additionally, the following tests can also be performed if deemed necessary at the discretion of the operator performing the tests: 8) ventricular and/or atrial direct current (D.C.) leakage; 9) alternating current (A.C.) interference test; 10) battery drain test; and, 11) ventricular frequency response test. These tests are discussed in greater detail below.
Implementing either of the above testing procedures the ECRI procedures or the manufacturer's procedures is a very time consuming process requiring several pieces of testing equipment, including a function generator, oscilloscope, and multimeter. Comprehensive testing of an external cardiac pacemaker under these conditions requires that the pacemaker be returned to the clinical engineering laboratory and generally requires at least an hour and a half of testing time per pacemaker.
Attempts have been made in the art to improve the ease and efficiency of testing cardiac pacemakers. However, these attempts have been for the most part directed only to limited as opposed to comprehensive testing and have been generally limited to implantable type cardiac pacemakers.
For example, the prior art includes several separate systems designed to test either only individual parameters of cardiac pacemakers or discrete circuits. Examples include: U.S. Pat. No. 4,021,736, issuing May 3, 1977 to Walters et al. directed to a circuit for measuring the refractory period; U.S. Pat. No. 4,256,114, issuing Mar. 17, 1981 to Carlson et al. also directed to measuring refractory intervals; U.S. Pat. No. 4,263,548, issuing Apr. 21, 1981 to Bartelt et al. directed to measuring amplitude; and U.S. Pat. No. 4,295,468, issuing Oct. 20, 1981 to Bartelt directed to measuring R wave sensitivity. While these advances in the art may have improved the evaluation of pacemakers, they have not provided for a means to comprehensively and expeditiously test pacemakers outside of the laboratory setting.
Daniel J. Coiro, "An External Demand Pacemaker Evaluation System", Journal of Clinical Engineering, Vol. 14, No. 1, pp. 49-54 (1989), describes a test device to facilitate the evaluation of external demand pacemakers. Coiro's device eliminates some of the additional circuitry needed, but still requires an oscilloscope and is not easily portable.
A portable pacemaker testing device is available from Environics Adaptive Technology, Inc., of Newton, Mass., under the "QUICK-CHEK".TM. mark. However, this device is capable of performing only superficial testing and does not provide a full evaluation of an external pacemaker as specified by the manufacturers of many pacemakers or by ECRI.
Environics Adaptive Technology, Inc. also markets a personal computer-based external pacemaker analyzer under the mark PACE-ALYZER.TM.. This product consists of an add-on card for a personal computer, and associated software under the mark PACE-SOFT.TM.. However, this product is not self-contained or portable, does not perform all of the tests necessary to comprehensively test medical pacing units, and requires the user to obtain and incur the additional expense of the necessary personal computer which in most applications is not battery-powered or portable.
Thus, a need exists in the art for a portable, self-contained comprehensive medical pacer testing device that expedites the complete analysis of all critical medical pacer parameters.
There also exists a need in the art for medical pacer testing devices which permit the analysis of all critical medical pacer parameters in clinical care or other settings in order to eliminate the need to return the pacer to the laboratory for comprehensive testing.